Field of the Invention
The present invention relates to a display device having a touch sensor, and more particularly to a display device that divides a period of time and alternately drives a touch sensor and a display area, thereby reducing the occurrence of noise and sensing time, and a method of driving the same.
Discussion of the Related Art
In recent years, a touch sensor (e.g. a touch screen or a touch panel) enabling information to be input by a touch on screens of various kinds of display devices has been widely used as an information input device for computer systems. The touch sensor enables a user to simply touch a screen through a finger or a stylus to move or select information displayed on the screen. Consequently, people of all ages and both sexes can easily use the touch sensor.
The touch sensor senses a touch position on the screen of a display device and outputs touch information. A computer system analyzes the touch information and executes a command. A flat display panel, such as liquid crystal display panel, a plasma display panel and an organic light emitting diode display panel, is mainly used as the display device.
Based on the sensing principle thereof, the touch sensor may be of a resistance film type, a capacitive type, an optical type, an infrared rays type, an ultrasonic type or an electromagnetic type. Generally, the touch sensor is manufactured in the form of a panel, which is attached to the top of a display device to perform a touch input function. However, the touch panel is manufactured separately from the display device, resulting in increased manufacturing cost. In addition, the total thickness and weight of the display device are increased. As a result, the mobility of the display device is deteriorated. Furthermore, the display device is restricted in design.
To solve the above problem, in recent years, an in-cell touch sensor formed by placing a touch sensor in a display panel, such as a liquid crystal display panel and an organic light emitting diode display panel, has been developed. A photo touch sensor to recognize a touch according to luminous intensity using a phototransistor or a capacitive touch sensor to recognize a touch according to capacitive variation is mainly used as the in-cell touch sensor.
The photo touch sensor recognizes a touch based on photo leakage current of the phototransistor generated from light incident upon or reflected from a touch body. The capacitive touch sensor recognizes a touch based on variation of capacitance generated when a small amount of electric charge moves to a touch point when a conductive body, such as a human being or a stylus, makes a touch.
In the touch sensor attached on the conventional display device, the display device and the touch sensor are driven independently, and therefore, the display device and the touch sensor can be driven at the same time. In the in-cell type touch sensor mounted in a pixel array of the display device, however, it is not possible to drive the display device and the touch sensor at the same time. Therefore, there is a necessity for a novel method of driving the display device having the in-cell type touch sensor.